1. Field of the Invention
This invention relates to an overfill alarm assembly for a storage tank. More specifically, an assembly according to the invention is configured to be installed as an in-line module with a vent pipe in a vented storage tank for liquids such as waste oil or gasoline.
2. Description of the Prior Art
In large tanks of the type that are used to store expandable liquids such as waste oil or gasoline, such as the tank disclosed in U.S. Pat. No. 5,033,637 to Webb, it is desirable to provide a vent pipe for preventing excessive pressure build-up within the tank. Venting is required in practically all states and countries.
It is further desirable in such systems to have some type of system for indicating when the liquid within the storage tank reaches a predetermined level. With such an indicating system, overfilling of the storage tank can be prevented.
To mount a vent pipe or an overfill sensing system to a storage tank, it is typically necessary to form a number of threaded openings in a top surface of the tank. However, it is generally recognized that the number of holes or openings in the tank should be kept to a minimum, particularly when storing volatile substances such as gasoline or kerosene.
Most storage tanks presently in use include a vent pipe that is threaded into an opening in the top surface of the storage tank, but do not include an overfill indicating system. It is clear that there is a need in the prior art for an overfill sensing and alarm assembly that could be used in such systems without the necessity for forming an additional hole in the storage tank.